This Spaghetti Squash Stuffed Portabella dish turn a handful of simple vegetables into a satisfying meatless meal. Roasted portabella mushroom caps are filled with tender spaghetti squash, sweet sautéed onion, juicy tomatoes, and fresh greens, then finished with mozzarella and crisp panko crumbs. It takes a little oven time, but the hands-on work is simple and most of the ingredients are easy to find.

💬 Why This Recipe Works in My Kitchen

This recipe started as a shop-the-fridge dinner when I had spaghetti squash and portabella but no real dinner plan. Combining them gave me a fresh way to use spaghetti squash without treating it like pasta, and the finished mushrooms were hearty enough to serve as the main dish.

• It turns basic produce into a complete-looking meal.
• The squash filling is light, while the mushroom cap gives each serving a satisfying, savory bite.
• Fresh tomatoes create a simple sauce without needing a jarred sauce.
• Mozzarella and panko add the melty, crisp finish that keeps the vegetables from feeling plain.
• Most of the cooking is hands-off roasting, so a beginner can prepare the filling while the oven does the heavy lifting.

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Ingredients

Fresh Ingredients

• medium spaghetti squash
• yellow onion, chopped
• fresh tomatoes, chopped
• spinach, kale, or chard 
• large portabella mushroom caps

Pantry Ingredients

• extra-virgin olive oil
• salt
• black pepper
• panko breadcrumbs

Refrigerated Ingredients

• shredded mozzarella cheese

The exact amounts are included in the recipe card 

Stuff the mushrooms with the vegetable mixture.

Layer on the cheese and panko crumbs before baking.

Why This Recipe Works

Roasting the portabellas before filling them allows much of their moisture to escape, which helps prevent a watery final dish. The tomatoes supply acidity and enough juice to bring the squash strands together, while the mixed greens add color and freshness. Mozzarella gives the filling richness and helps the panko stay in place as it browns.

Substitutions and Variations

• Use a shortcut squash: Replace the whole squash with refrigerated or frozen cooked spaghetti squash when available. Drain and pat it dry before adding it to the skillet because packaged squash may hold more water.

• Swap the cheese: Try provolone, fontina, Parmesan, or an Italian cheese blend. Parmesan adds flavor but does not melt as generously, so combine it with mozzarella if you want a stretchy top.
• Make it gluten-free: Use gluten-free panko or crushed gluten-free crackers.
• Add protein: Stir cooked Italian sausage, shredded chicken into the filling. If adding meat, reduce the squash slightly so the caps are not overloaded.

If you want another mushroom-forward dinner, my Freekeh with Mushrooms and Asparagus offers a chewy whole-grain option with plenty of vegetables.

How to Keep Stuffed Portabellas from Getting Watery

• Pre-roast the caps: Mushrooms contain a great deal of water. Roast them before stuffing and drain the pan before adding the filling.
• Do not soak mushrooms: Wipe them with a damp towel instead of placing them under running water for a long time.
• Drain the squash: If the cooked squash seems wet, spread the strands on a clean towel and gently blot them.
• Cook off excess tomato juice: The tomatoes should make a light coating, not a puddle. If the skillet looks watery, simmer another minute before adding the squash.
• Serve after a short rest: Five minutes lets the cheese settle, but a long wait gives the vegetables more time to release moisture.

Beginner Cook Checkpoints

• Squash is ready: A fork easily separates the flesh into strands without hard, crunchy areas.
• Mushrooms are pre-roasted: The caps have softened, look darker, and have released liquid into the pan.
• Onion is cooked: The pieces are soft and translucent, not browned or crisp.
• Filling is balanced: It is moist enough to hold together but there is no loose liquid pooling in the skillet.
• Finished dish: The cheese is fully melted, the panko has some golden color, and the center is hot.

Storage and Reheating

•  Refrigerate: Cool the stuffed mushrooms, then store them in a covered container for up to 3 days.
• Store separately when possible: For meal prep, refrigerate the roasted caps and squash filling in separate containers. Fill and bake them when ready to eat for a less watery result.
• Reheat in the oven: Place the mushrooms in a baking dish and warm at 350°F for 15 to 20 minutes, or until hot in the center. Cover loosely at first if the topping is already brown.
• Reheat in the microwave: Heat one serving in short intervals until hot. The topping will soften, but the flavor will still be good.
• Freezing: Freezing is not the best choice because both mushrooms and spaghetti squash can become watery after thawing.

Ways to Serve It and Make It a Complete Meal

• Keep it simple: Serve one stuffed mushroom with a crisp green salad and lemon vinaigrette.
• Add a protein: Pair it with roasted chicken, turkey meatballs, or white beans for a more filling meal.
• Add bread: Garlic toast or a small piece of crusty bread is useful for catching the tomato and mushroom juices.
• Add a bright side: A fresh tomato-based salad balances the roasted vegetables and melted cheese.

For that bright side, try my Tomato and Olive Salad with Lemon Olive Oil Dressing; its lemony dressing will cut through the mozzarella nicely.

Spaghetti Squash Stuffed Portabellas

This spaghetti squash stuffed portobello mushrooms recipe make vegetables feel like the main event. The beginner-friendly recipe walks you through roasting the squash, draining the caps, and getting a golden cheesy topping.

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Easy Dinners

Cuisine: American

Prep Time: 10 minutes mins

Cook Time: 1 hour hr 10 minutes mins

Total Time: 1 hour hr 20 minutes mins

Servings: 4

Author: Celeste @TheWholeServing

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Ingredients

• 1 medium spaghetti squash
• 1 tablespoon extra virgin olive oil plus 3 ½ teaspoons more for brushing squash and mushrooms before roasting
• ¾ cup chopped yellow onion
• 1 cup chopped fresh tomatoes
• salt and pepper to taste
• 2 cups loosely packed greens of your choice, spinach, kale, or chard 
• 4 portabella mushrooms
• ¾ cup shredded mozzarella cheese
• 4 tablespoons Panko bread crumbs

Instructions

• Heat the oven and prepare the spaghetti squash. Preheat the oven to 400°F. Carefully cut off the top and bottom of the squash then cut the spaghetti squash lengthwise from top to bottom. Scoop out the seeds from each half. Drizzle with olive oil and sprinkle with salt and pepper. Place the halves cut side down on a parchment-lined baking sheet and roast for 35 to 45 minutes, or until the flesh pulls away in tender strands when scraped with a fork. Let it cool until it is safe to handle, then pull the squash into strands and set aside.

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• Prepare the mushrooms while the squash roasts. Gently wipe the portabellas clean with a damp paper towel. Twist out the stems. Use a spoon to scrape out the dark gills if you prefer a lighter-looking filling. Brush both sides lightly with olive oil and place the caps open-side down in a rimmed baking pan.
• Roast the mushroom caps. When the squash comes out, keep the oven at 400°F. Roast the mushrooms for about 10 minutes, turn them open-side up, and roast 8 to 10 minutes more. They should look slightly softened and release some liquid. Carefully pour or blot away that liquid so the filling does not become watery.
• Cook the onion. Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add the chopped onion and cook for 3 to 4 minutes, stirring often, until it looks translucent, which means softened and slightly see-through.
• Add the tomatoes. Stir in the chopped tomatoes and cook for about 3 minutes. They should soften and release enough juice to lightly coat the bottom of the pan.
• Add the spaghetti squash. Add the cooked squash strands to the skillet and toss until the vegetables are evenly combined. Cook for 1 to 2 minutes, just until heated through. Season with salt and black pepper to taste.
• Wilt the greens. Remove the skillet from the heat. Stir in the spinach, kale, and chard mix. The greens will soften from the heat of the filling. If the mix includes sturdy kale or chard pieces that stay firm, return the pan to low heat for 1 to 2 minutes.
•  Fill the mushroom caps. Divide the squash mixture evenly among the four roasted portabellas. Do not pack the filling down tightly. Sprinkle each cap with mozzarella, then top each with 1 tablespoon panko.
• Bake until melted and crisp. Return the stuffed portabellas to the oven for 10 to 12 minutes, or until the cheese is melted and the panko is lightly golden. If you want deeper browning, broil for 30 to 60 seconds while watching closely.
• Cool briefly and serve. Let the mushrooms rest for about 5 minutes. They will be very hot and may release a little more juice as they sit.

Nutrition

Serving: 4mg | Calories: 194kcal | Carbohydrates: 20.7g | Protein: 9.1g | Fat: 9.9g | Saturated Fat: 4g | Cholesterol: 18.7mg | Sodium: 134.8mg | Fiber: 4.4g | Sugar: 7.1g

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